all-posts page, page titles, index page

src/components/Post.astro

@@ -10,8 +10,8 @@ import { formatDate } from '@lib/datefmt';
 
 export interface Props {
     entry: CollectionEntry<'posts'>,
-    prevSlug: string | null,
-    nextSlug: string | null,
+    prevSlug?: string | null,
+    nextSlug?: string | null,
 };
 
 const { entry, prevSlug, nextSlug } = Astro.props;